What is the 2,4-DNP test?

The reagent $2,4$-dinitrophenylhydrazine (also called Brady’s reagent) is used to test for the presence of a carbonyl group in aldehydes and ketones.

Reaction involved

Aldehydes and ketones react with $2,4$-DNP to form 2,4-dinitrophenylhydrazones, usually giving a yellow/orange precipitate:

$\text{RCHO or RCOR'} + \text{2,4-DNP} \rightarrow \text{hydrazone precipitate}$

Check each option

• A: ether — Ethers do not contain a carbonyl group, so they do not give the $2,4$-DNP test.
• B: amine — Amines also do not contain a carbonyl group, so they do not give this test.
• C: aldehyde — Aldehydes contain the carbonyl group $(-CHO)$, so they do give the $2,4$-DNP test.
• D: halogens — Halogens are identified by different tests, not by $2,4$-DNP.

Conclusion

Since this is a single-correct MCQ, the correct option is:

$\boxed{\text{C: aldehyde}}$

Comparison with stored correct answer

Stored correct answer = C

Derived answer = C

Therefore, the derived answer agrees with the stored correct answer.